I realise a strange behaviour of several FreeBSD 8.0-STABLE/amd64 boxes.
All boxes have the most recent STABLE. One box is a UP system, two
others SMP boxes, one with a Q6600 4-core, another XEON with 2x 4-cores
(Dell Poweredge III).

Symptome: All boxes have ZFS and UFS2 filesystems. Since two weeks or
so, sometimes the I/O performance drops massively when doing 'svn
update', 'make world' or even 'make kernel'. It doesn't matter what
memory and how many cpu the box has, it get stuck for several seconds
and freezing. On the UP box, this is sometimes for 10 - 20 seconds.
A very interesting phenomenon is the massively delayed file writing on
ZFS filesystems I realise. Editing a file in 'vi' running on one XTerm
and having in another Xterminal my shell for compiling this file, it
takes sometimes up to 20 seconds to get the file updated after it has
been written. It's like having an old, slow NFS connection with long
cache delays.
These massively delayed file transactions are not necessarely under
heavy load, sometimes they occur in a relaxed situation. They seem to
occur much more often on the UP box than on the SMP boxes, but this
strange phenomenon also occur on the Dell Poweredge II, which has 16GB
RAM and summa summarum 16 cores. This phenomenon does occur on ZFS- and
UFS2 filesystems as well. It is hardly reproducable.

The discussion then focuses on :

Quote:

The disks involved don't happen to be Western Digital Green Power disks,
do they? The Intelli-Park function in these disks are wrecking havoc
with I/O in Linux-land at least, causing massive stalls and iowait
through the roof during the 25-30 seconds it takes for the heads to
unload after parking. I have two of these disks sitting on my desk now
collecting dust...

Althoug the OP did not use these disks, still a very interesting read

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Last edited by J65nko; 20th January 2010 at 10:35 PM.
Reason: boldfacing the disk type

We (now) have these disks in our ZFS storage server, and things are starting to go downhill. They were just too good of a bargain to pass up (~$100 CDN for 1.5 TB drives, over $200 CDN for the RE 1.5 TB drives). Now we realise that you get what you pay for.

In under 6 weeks of usage, some of the drives are showing almost 40,000 Load Cycles. At that rate, we'll be past the 300,000 mark within a year, possibly 18 months.

Things were running fine until this week. Out of 8 drives in one raidz2 vdev, we've successfully replaced 5. The resilver process took ~60 hours to complete for each drive.

Last Friday, I replaced the 6th drive, and it still hasn't finished the resilver. It's averaging 1-3 GB per hour. Throughput on the entire pool has dropped to 9 MBps ... even after a reboot. It's just nuts! Any zfs/zpool operations except list/status takes multiple minutes to complete. Even unmounting a snapshot takes upwards of 10 minutes.

Our lovely backup process that used to process ~110 servers in under 11 hours barely complete a third of that now. I'm about ready to start re-replacing these drives with the original 500 GB WD Caviar Blue and Caviar Black drives.

Also, and very importantly, this drive is not for RAID systems. To keep with the low-power design, Western Digital chose to automatically park the drive heads at times, which some RAID systems will see as a hard drive failure. So you could be in a constant RAID rebuild if the drives are mirrored, or if the drives are in RAID-5 for parity, you could lose all of your data. WD has acknowledged this, and released the RE4-GP 2TB hard drive for users who need big RAID arrays. They are really pricey though, so you may want to stick with a 1TB Caviar Black for your RAID solutions.

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Green drives from WD have a variable speed motor that can go as high as 7200 or as low as ... who knows.

The most annoying thing is that the "idle timeout" to park the heads is ... 8 seconds. In a desktop drive!! Talk about unnecessary wear and tear on the drive. Just browsing the web will causes the drive to thunk about, since Firefox has a 30s (or 10s?) "update the open tabs list" timer. So if you read a page for more than 8s, the drive will park.

I can understand having that feature in a laptop drive, where you don't want to be spinning the drive unless absolutely necessary. But in a desktop drive?

Contrary to the vast majority of online reports ... one can use the wdidle3 utility to "disable" this horrible idle timeout setting.

While one cannot truly disable it, one can set the timeout to 62 minutes, effectively disabling it. Or select a value that reflects your workload.

I've "disabled" this on the 7 drives that have been put into our storage server. The resilver throughput for that 7th drive has jumped from an average of 7 MBps to an average of 40 MBps!!

Checking the Load_Cycle_Count via smartctl now shows the numbers as not moving. Previously, they would go up quite quickly (1 drive has 50,000 after less than 2 months of use). Even using a twiddle script running every 5 seconds wouldn't completely stop this from increasing.

Unfortunately, the wdtler utility does not work on these drives. But it's still an improvement. So maybe they aren't totally worthless drives.

OK, this is interesting information. I've been planning on moving my storage on my home file server to a fairly large raidz2 config for some time but hasn't gotten around buying the drives and doing it.
I guess to aviod future headaches, it's best to stay away from anything with "green" in it.
To bad, they are usually a pretty good bargain.
(I remember seeing part of this discussion in the mailling list archives, but must have missed the last bit.)

There's also the WD15EARS, which has 64MB cache (Which is near-useless AFAIK) and so called "Advanced format", which seems to be some sort of marketing speak for a 4K sector size.

Is there any advantage for a 4K sector size instead of the default 512 bytes? I know about the disk alignment (Start at 64, not 63), but is there are real world benefit or drawback?

(It's also 15 euro's more expensive)

Most importantly however, the WD site mentions:

Quote:

This firmware modifies the behavior of the drive to wait longer before positioning the heads in their park position and turning off unnecessary electronics. This utility is designed to upgrade the firmware of the following hard drives: WD1000FYPS-01ZKB0, WD7500AYPS-01ZKB0, WD7501AYPS-01ZKB0.
CAUTION: Do not attempt to run this software on any hard drives other than what is listed above.

It's not entirely clear to me if this utility only works for listed models or for all GP drives (including the WD15EADS/EARS drives)?

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Is there any advantage for a 4K sector size instead of the default 512 bytes?

Here You have detailed comparision between WD10EADS and WD10EARS:http://tomshardware.com/reviews/wd-4k-sector,2554.html

Quote:

Originally Posted by Carpetsmoker

It's not entirely clear to me if this utility only works for listed models or for all GP drives (including the WD15EADS/EARS drives)?

According to phoenix it does work:http://forums.freebsd.org/showpost.php?p=98908&postcount=21

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There's also the WD15EARS, which has 64MB cache (Which is near-useless AFAIK) and so called "Advanced format", which seems to be some sort of marketing speak for a 4K sector size.

Is there any advantage for a 4K sector size instead of the default 512 bytes? I know about the disk alignment (Start at 64, not 63), but is there are real world benefit or drawback?

Skip all the WD "Advanced Format" drives. They're crap. They report a 512 KB physical sector size to the OS, even though they use a 4 KB physical sector size. This causes all kinds of performance issues for everything.

4 KB drives from other manufacturers correctly report the real physical sector size, so the OS/filesystem will work correctly.